About this 3D model

This is going to be a reaaaal long one, folks. Better buckle up your thingibelts. I believe this project is complete. There are workable, though probably not ideal, solutions to all major problems. The code and mount are both perfectly usable. Youtube videos availabe at: http://www.youtube.com/watch?v=tSp8FKgoY8k http://www.youtube.com/watch?v=mv3wxvR8w5A New! http://www.youtube.com/watch?v=XafKYIxlgBk For people who just want the short version to go with the photos: Of course when I thought about what to print first, I thought the classic 20mm cube, but in a checkerboard pattern. Setting the head offsets in the software exactly is important, and not difficult, but I couldn't dial it in during the course of this project as every time I'd set it I'd change something to unset it again. That's the only reason many of the prints are overlapping in odd ways. Any ooze tends to accumulate at the offset position and eventually get rolled into the model, making a mess. The final update to the script has solved this with some ooze-controlling reversal, which I didn't bother to get dialed in exactly before closing this file. :) THE STORY: On Friday, it struck me I had a MK5 hot end just sitting here in a box, unusued, and I thought -- wouldn't two extruders in one machine be a neat idea? You could print two colors together, or you could use one to print some kind of support material; who knows what that might be. I knew you could dissolve PLA with toxic chemicals, but I also knew I'd never be allowed to play with toxic chemicals; I'm not even really allowed to print ABS. I decided I would have the entire project complete, from conception to completion, done by the end of the weekend. You might have noticed my rash of part releases. Well, I missed it by /that/ much, but it turns out to be good news. MBI on Monday announced dissolvable plastic ( http://store.makerbot.com/makerbot-pva.html )... which means now we know what to use as support material. The timing could not be more perfect. In addition, this makes the perfect thing to do with your old MK5 once you also have a shiny new MK6... Or maybe you bought a third-party hot end, like one of the excellent ones from Makergear.com, and now you can get your old stock hot end out of its drawer and use it again. Now, when I say completion, I don't mean this project is finished, oh no. There's a very long list of little things to fix or change, and a short list of big things to fix or change. CURRENT MAJOR PROBLEMS: * The bolts on the build platform mean your print area can be greatly reduced -- -- SOLVED... switching to the ABP cures this problem neatly. * Need a brilliant way to assure both heads are on the same Z-plane physically. -- SOLVED... not exactly brilliant, but the new mount is easily adjustable. CURRENT MINOR PROBLEMS: * It would be helpful to people who do not have the option of switching to the ABP to have a mount where the heads are aligned 90 degrees offset from this. * Some kind of quick-release mount for the second extruder would be nice. Maybe there would be a way to work Z-height adjustment into it. -- SOLVED: V2 mount is easy to remove and install separately. * The closer the two heads together can be brought together, the less loss of build area will happen, bolts or no bolts. * It should be theoretically possible to drive two heads from one EC; if I blow up my other MOSFET I may have to pursue this possibility myself. This would require some hacking of RepG at the least and probably the firmware too. * The software could use many improvements; what I've given here is a workable starting point to build from. TRIALS AND TRIBULATIONS: I nearly hit my goal of having it all wrapped up by the weekend. I missed it because the 608-based Wade's style extruder I built off the STLs I uploaded over the weekend: http://www.thingiverse.com/thing:6492 did not work. It wouldn't push plastic. You might think that meant it worked OK, I just couldn't demo it, and you'd be right. At this point, I had two stepper extruders working in concert but I couldn't make a test print, because one wouldn't push plastic. I felt like I couldn't put up the thingiverse entry until I could make the thumbnail a two-tone print. So, this set me back a whole day. Well, this, and the fact that I have to work for a living, still... I decided the problem was the bolt I hobbed wasn't nearly as good as Makerbot's MK5 drive gear thingy: http://store.makerbot.com/mk5-drive-gear.html ... while the MBI delrin extruder is of questionable value, this gear is the /bomb/. I tried hobbing another bolt, but I just couldn't make one that worked. An additional problem is that the design STLs I posted have the wrong value for the filament distance from the hobbed bolt, making it add a lot of friction and nearly impossible to get in the hole. So I decided that other people would want to use it with the DC motor, and I might as well buckle down and replace my 2nd stepper extruder with a DC extruder, temporarily